Change test pattern of writing to existing files

Many tests were writing to temporary files that already exist, which is
not a supported workflow.

glymur/jp2k.py

@@ -851,12 +851,17 @@ def _write(self, img_array):
         in memory.
         """
         if version.openjpeg_version < '2.3.0':
-            msg = ("You must have at least version 2.3.0 of OpenJPEG "
-                   "in order to write images.")
+            msg = (
+                "You must have at least version 2.3.0 of OpenJPEG in order to "
+                "write images."
+            )
             raise RuntimeError(msg)
 
         if hasattr(self, '_cparams'):
-            msg = "You cannot write image data to a JPEG 2000 file that already exists."
+            msg = (
+                "You cannot write image data to a JPEG 2000 file "
+                "that already exists."
+            )
             raise RuntimeError(msg)
 
         self._determine_colorspace()

tests/test_cinema.py

@@ -76,9 +76,8 @@ def test_cinema2K_bad_frame_rate(self):
 
         EXPECTED RESULT:  ValueError
         """
-        with open(self.temp_j2k_filename, mode='wb') as tfile:
-            with self.assertRaises(ValueError):
-                Jp2k(tfile.name, data=self.jp2_data, cinema2k=36)
+        with self.assertRaises(ValueError):
+            Jp2k(self.temp_j2k_filename, data=self.jp2_data, cinema2k=36)
 
     def test_NR_ENC_X_6_2K_24_FULL_CBR_CIRCLE_000_tif_17_encode(self):
         """